This invention relates to a surround reproducing technique using a speaker array.
A speaker array apparatus of a delay array system uses a technique of outputting the same audio signals with a gradually different delay times given so as to arrive at the spatial focus at the same time from a plurality of speakers placed on a line or on a plane, thereby strengthening the acoustic energy on the periphery of the focus by common mode addition and consequently producing a sound beam having strong directivity in the focus direction. The speaker array apparatus performs such delay processing for each of audio signals of multiple channels (for example, C: Center, FL: Front Lch, FR: Front Rch, SL: Rear Lch, and SR: Rear Rch) and adds the signals subjected to the delay processing in all channels and supplies the result to the speakers, whereby it can provide different directivity for sound beams relating to multiple channels and can output at the same time (for example, Patent Document 1).
Using the technique as shown in Patent Document 1, a related speaker array apparatus 1000 can reflect sound beams on wall faces of a room 100 and can cause the sound beams relating to each channel to arrive at a listening position, as shown in FIG. 6. Accordingly, a sound image is localized in the wall face direction, and a listener 200 at the listening position can perceive a sound as if the sound is produced from virtual speakers 300-FL, 300-FR, 300-SL, and 300-SR in addition to the front speaker array apparatus 1000, for example, so that a good surround effect can be provided.
[Patent document 1] US2007/0230724A1
If a wall face exists at a position just behind the listener 200 (the lower side in the figure) (see FIG. 4A) or if a wall face does not exist behind the listener or the like, the related speaker array apparatus 1000 may be unable to cause the sound beams to arrive at the listening position using reflection on the wall face behind the listener 200. In such a case, sound images cannot be localized behind the listener 200. Therefore, the speaker array apparatus 1000 mixes the channels SL and SR to be localized behind the listener 200 with the channels FL and FR respectively to localize in the direction of the virtual speakers 300-FL and 300-FR. Thus, the surround effect may be weakened.